Multi-layer transparent structures for electronic device housings

ABSTRACT

Transparent structures for portions of electronic device housings are disclosed. The transparent structures are formed from multiple layers of transparent (optically clear) materials. The multiple layers can include at least an outer glass layer and one or more other transparent layers that can be either glass or polymer layers. The multiple layers can be bonded together with one or more lamination layers. Accordingly, multi-layer transparent structures that are formed from multiple layers bonded together are able to be not only thin but also sufficiently strong and resistant to damage. The multi-layer transparent structures are well suited for use in consumer products, such as consumer electronic devices (e.g., portable electronic devices).

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation patent application of U.S. patentapplication Ser. No. 13/249,038, filed Sep. 29, 2011 and titled“Multi-Layer Transparent Structures for Electronic Device Housing”, thedisclosure of which is hereby incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

Conventionally, some portable electronic devices use glass as a part oftheir devices, either internal or external. Externally, a glass part canbe provided as part of a housing, such a glass part is often referred toas a cover glass. The transparent and scratch-resistance characteristicsof glass make it well suited for such applications. Internally, glassparts can be provided to support display technology. More particularly,for supporting a display, a portable electronic device can provide adisplay technology layer beneath an outer cover glass. A sensingarrangement can also be provided with or adjacent the display technologylayer. By way of example, the display technology layer may include orpertain to a Liquid Crystal Display (LCD) that includes a Liquid CrystalModule (LCM). The LCM generally includes an upper glass sheet and alower glass sheet that sandwich a liquid crystal layer therebetween. Thesensing arrangement may be a touch sensing arrangement such as thoseused to create a touch screen. For example, a capacitive sensing touchscreen can include substantially transparent sensing points or nodesdispersed about a sheet of glass or plastic.

Unfortunately, however, use of glass with portable electronic devicesrequires that the glass be relatively thin. Generally speaking, thethinner the glass the more susceptible the glass is to damage when theportable electronic device is stressed or placed under a significantforce. Chemically strengthening has been used to strengthen glass. Whilechemically strengthening is effective, there is a continuing need toprovide improved ways to provide cover glass that is thin andsufficiently strong to resist breakage.

SUMMARY

The invention relates to transparent structures for portions ofelectronic device housings. The transparent structures are formed frommultiple layers of transparent (optically clear) materials. The multiplelayers can include at least an outer glass layer and one or more othertransparent layers that can be either glass or polymer layers. Themultiple layers can be bonded together with one or more laminationlayers. Accordingly, multi-layer transparent structures that are formedfrom multiple layers bonded together are able to be not only thin butalso sufficiently strong and resistant to damage. The multi-layertransparent structures are well suited for use in consumer products,such as consumer electronic devices (e.g., portable electronic devices).

The invention can be implemented in numerous ways, including as amethod, system, device, or apparatus. Several embodiments of theinvention are discussed below.

As an electronic device, one embodiment can, for example, include atleast an outer housing for the electronic device, and a plurality ofelectrical components provided within the outer housing. At least aportion of the outer housing can include at least a multi-layer housingstructure. The multi-layer housing structure can include a first layer,a lamination layer, and a second layer. The first layer and second layercan be laminated together via the lamination layer.

As a consumer electronic product, one embodiment can, for example,include at least: a housing having a front surface, a back surface andside surfaces; electrical components provided at least partiallyinternal to the housing, the electrical components including at least acontroller, a memory, and a display, the display being provided at oradjacent the front surface of the housing; and a multi-layer coverstructure provided at, over or in the front surface of the housing suchthat it is provided over the display. The multi-layer cover structurecan include a first layer, a lamination layer and a second layer, andthe first layer and second layer can be laminated together via thelamination layer.

As a method for forming a laminated glass structure, one embodiment can,for example, include at least the acts of: obtaining an outer glasslayer, chemically strengthening the outer glass layer, obtaining atransparent layer, obtaining a lamination layer, and laminating thetransparent layer to the outer glass layer via the lamination layer toform the laminated glass structure.

As a method for forming a laminated glass structure, one embodiment can,for example, include at least the acts of: obtaining a first glasslayer, chemically strengthening the first glass layer, obtaining asecond glass layer, chemically strengthening the second glass layer,obtaining a lamination layer, and forming the lamination glass structurefrom the first glass layer, the lamination layer and the second glasslayer.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements, and in which:

FIG. 1 is a simplified view of a multi-layer housing structure accordingto one embodiment.

FIGS. 2A-20 illustrate assembly of a multi-layer housing structureaccording to one embodiment.

FIG. 3 is a flow diagram of a lamination process according to oneembodiment.

FIG. 4 is a flow diagram of a lamination process according to anotherembodiment.

FIG. 5 is a simplified view of a multi-layer housing structure accordingto another embodiment.

FIG. 6A is a simplified view of a multi-layer housing structureaccording to another embodiment.

FIG. 6B is a simplified view of a multi-layer housing structureaccording to another embodiment.

FIG. 6C is a simplified view of a multi-layer housing structureaccording to another embodiment.

FIG. 7 is a cross-sectional view of an electronic device housingaccording to one embodiment.

FIG. 8 is a perspective diagram of a handheld electronic deviceaccording to one embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention relates to transparent structures for portions ofelectronic device housings. The transparent structures are formed frommultiple layers of transparent (optically clear) materials. The multiplelayers can include at least an outer glass layer and one or more othertransparent layers that can be either glass or polymer layers. Themultiple layers can be bonded together with one or more laminationlayers. Accordingly, multi-layer transparent structures that are formedfrom multiple layers bonded together are able to be not only thin butalso sufficiently strong and resistant to damage. Since the transparentstructures include at least one glass layer, the transparent structurescan also be referred to as glass articles (or multi-layer glassarticles). The multi-layer transparent structures are well suited foruse in consumer products, such as consumer electronic devices (e.g.,portable electronic devices).

Embodiments of the invention can relate to apparatus, systems andmethods for improving strength of a glass article for a consumerproduct, such as a consumer electronic device. In one embodiment, theglass article may be an outer surface of a consumer electronic device.For example, the glass article may, for example, correspond to a glasscover that helps form part of a display area of the electronic device(i.e., situated in front of a display either as a separate part orintegrated within the display). As another example, the glass articlemay form a part of a housing for the consumer electronic device (e.g.,may form an outer surface other than in the display area). In anotherembodiment, the glass article may be an inner component of a consumerelectronic device. For example, the glass article can be a componentglass piece of a LCD display provided internal to the housing of theconsumer electronic device.

The apparatus, systems and methods for improving strength of thin glassarticles are especially suitable for glass covers or displays (e.g., LCDdisplays), particularly those assembled in small form factor electronicdevices such as handheld electronic devices (e.g., mobile phones, mediaplayers, personal digital assistants, remote controls, etc.). The glassarticles can be thin in these small form factor embodiments, such asless than 3 mm, or more particularly between 0.3 and 2.5 mm. Theapparatus, systems and methods can also be used for glass covers ordisplays for other devices including, but not limited to, relativelylarger form factor electronic devices (e.g., portable computers, tabletcomputers, displays, monitors, televisions, etc.). The glass articlescan also be thin in these larger form factor embodiments, such as lessthan 5 mm, or more particularly between 0.3 and 3 mm.

Embodiments of the invention are discussed below with reference to FIGS.1-8. However, those skilled in the art will readily appreciate that thedetailed description given herein with respect to these figures is forexplanatory purposes as the invention extends beyond these limitedembodiments. The illustrations provided in these figures are notnecessarily drawn to scale; instead, the illustrations are presented ina manner to facilitate presentation.

FIG. 1 is a simplified view of a multi-layer housing structure 100according to one embodiment. The multi-layer housing structure 100 can,for example, be used as at least a portion of an outer housing for anelectronic device. More particularly, the multi-layer housing structure100 is well suited for use as at least a portion of an outer housing fora portable electronic device (specifically, compact portable electronicdevices).

The multi-layer housing structure 100 has a multi-layer structure. Inparticular, the multi-layer housing structure 100 includes a glass layer102 that provides an outer surface for the multi-layer housing structure100, and thus also for at least a portion of the outer housing for theelectronic device. The multi-layer housing structure 100 also includes alamination layer 104 as well as a transparent layer 106. The laminationlayer 104 serves to bond together the glass layer 102 and thetransparent layer 106. The bonding together of the glass layer 102 andthe transparent layer 106 via the lamination layer 104 can be denoted asa lamination, whereby the multi-layer housing structure 100 is formedfrom the lamination of the transparent layer 106 to the glass layer 102using the lamination layer 104.

Typically, the multi-layer housing structure 100 is to be opticallyclear or transparent. The glass layer 102 and the transparent layer 106are inherently optically clear or transparent. The lamination layer 104is also optically clear or transparent. Although it is desired that thedistinct layers of the multi-layer housing structure 100 be opticallyclear or transparent, it is understood that certain materials may not becompletely optically clear or transparent, thus, it is sufficient thatthese layers be substantially optically clear when formed into themulti-layer housing structure 100. Also, in some embodiments, thelamination layer 104 might be initially opaque before being activated tobond with other layers of the multi-layer housing structure 100;however, once the lamination layer 104 is activated, the laminationlayer 104 turns clear or transparent (at least substantially so).

The transparent layer 106 is typically an internal layer that does notform an outer user surface for the housing for the electronic device. Asa result, the transparent layer 106 can use different materialsdepending upon its particular product application. As an example, thetransparent layer 106 can correspond to a glass layer or can correspondto a polymer-based layer.

In one embodiment, the lamination layer 104 can be referred to as alamination film. The lamination layer 104 can pertain to any materialthat is suitable for lamination of the glass layer 102 with thetransparent layer 106. One example of a lamination material is polyvinylbutyral (PVB). PVB is a resin that provides strong binding, opticalclarity, adhesion to many surfaces, toughness and flexibility. Otherexamples of lamination materials include thermoplastic polyurethane(TPU).

FIGS. 2A-2C illustrate assembly of a multi-layer housing structureaccording to one embodiment. As illustrated, the multi-layer housingstructure being assembled is the multi-layer housing structure 100illustrated in FIG. 1.

In FIG. 2A, the glass layer 102 is depicted as a separate member. InFIG. 2B, the lamination layer 104 is placed adjacent the bottom surfaceof the glass layer 102. Thereafter, as shown in FIG. 2C, the transparentlayer 106 is placed adjacent the lamination layer 104. Once themulti-layer housing structure is arranged as illustrated in FIG. 2C, thelamination process which serves to bond the glass layer 102 to thetransparent layer 106 using the lamination layer 104 can be activated.In one implementation, the lamination process can be activated byplacing the multi-layer housing structure in a elevated temperatureenvironment (e.g., an oven). In another implementation, the laminationprocess can be activated by placing the multi-layer housing structure inan RF environment where radio frequency energy can be induced into thelamination layer 104 to activate the lamination process.

Although the widths of the glass layer 102, the lamination layer 104 inthe transparent layer 106 illustrated in FIGS. 2A-20 are shown as beingsame, it should be understood that the various layers need only beoverlapping and thus the width of the respective players can varydepending upon implementation. For example, the transparent layer 106could have a reduced width.

FIG. 3 is a flow diagram of a lamination process 300 according to oneembodiment. The lamination process 300 can operate to assemble or form alaminated structure, such as a laminated glass structure having at leastone glass layer.

The lamination process 300 initially obtains 302 an outer glass layer.The outer glass layer can serve as one side of the laminated structurecan be formed or assembled. The outer glass layer can then be chemicallystrengthened 304. By chemically strengthening the outer glass layer, theouter glass layer is better able to resist damage (such as breakage),such as when subjected to an impact event.

In addition, a transparent layer is obtained 306. The transparent layercan serve as an inner layer or an intermediate layer for the multi-layerstructure. The transparent layer can be formed of glass or can be formedof a polymer. A lamination layer can also be obtained 308. Thelamination layer is a thin layer of a material that can serve tolaminate together the outer glass layer to the transparent layer. Hence,the lamination process 300 then operates to laminate 310 the transparentlayer with the outer glass layer via the lamination layer, therebyforming a laminated structure. For example, the lamination layer can bebetween the outer glass layer and the transparent layer, and thenlamination can cause the lamination layer to bond to adjacent surfacesof the outer glass layer and the transparent layer.

To laminate 310 the transparent layer with the outer glass layer, thelamination layer typically needs to be activated, such as by heating thelamination layer or inducing energy (e.g., RF energy) into thelamination layer. The lamination serves to strongly bond, e.g., fuse,together the outer glass layer and the transparent layer. Following thelamination 310, the lamination process 300 is complete and can thereforeend.

FIG. 4 is a flow diagram of a lamination process 400 according toanother embodiment. The lamination process 400 can operate to assembleor form a laminated structure, such as a laminated glass structurehaving at least two glass layers.

The lamination process 400 can obtain 402 a first glass layer. The firstglass layer can then be chemically strengthened 404. By chemicallystrengthening the first glass layer, the first glass layer is betterable to resist damage (such as breakage), such as when subjected to animpact event.

In addition, as second glass layer can be obtained 406. Similarly, thesecond glass layer can be chemically strengthened 408. By chemicallystrengthening the second class layer, the second glass layer is betterable to resist damage (such as breakage), such as when subjected to animpact event. In one embodiment, the chemical strengthening 404 appliedto the first glass layer is performed to a different level, degree orstate than is the chemical strengthening applied to the second classlayer. In other words, it may be desirable to chemically strengthen thedifferent glass layers of the multi-layer housing structure in differentways. Specifically, in one example, the outer glass layer could bechemically strengthened to provide a relatively deep depth of layer,whereas an inner layer or the second glass layer can have a smallerdepth of layer but a higher compressive stress.

Still further, the lamination process 400 obtains 410 a laminationlayer. The lamination layer can be used to form 412 the laminated glassstructure from the first glass layer and the second glass layer afterthe laminated glass structure has been formed 412, the laminationprocess 400 can and.

FIG. 5 is a simplified view of a multi-layer housing structure 500according to another embodiment. The multi-layer housing structure 500includes three distinct glass layers that are laminated together to forma multi-layer structure that can be used as part of a housing for anelectronic device. The multi-layer housing structure 500 can include aglass layer 502 that can serve as an outer surface member for a portionof the multi-layer housing structure 500. A lamination layer 504 can beprovided between the glass layer 502 and a second glass layer 506. Thelamination layer 504 can serve to bond together a bottom layer of thefirst glass layer 502 and a top surface of the second class layer 506.In addition, a second lamination layer 508 can be provided between thesecond glass layer 506 and a third glass layer 510. The lamination layer508 can serve to bond together a bottom layer of the second class layer506 and a top layer of the third glass layer 510.

FIG. 6A is a simplified view of a multi-layer housing structure 600according to another embodiment. The multi-layer housing structure 600includes two distinct layers that are laminated together to form amulti-layer structure that can be used as part of a housing for anelectronic device. In particular, the multi-layer housing structure 600can include a first glass layer 602 that serves as an outer surfacemember for the multi-layer housing structure 600. In addition, alamination layer 604 can be provided between the first glass layer 602and a polymer layer 606. The lamination layer 604 can serve to bondtogether a bottom surface of the first glass layer 602 and a top surfaceof the polymer layer 606. The bonding provided using the laminationlayer 604 is stronger than an adhesive bond (e.g., pressure sensitiveadhesive).

FIG. 6B is a simplified view of a multi-layer housing structure 620according to another embodiment. The multi-layer housing structure 620includes two distinct glass layers and one polymer layer that arelaminated together to form a multi-layer structure that can be used aspart of a housing for an electronic device. The multi-layer housingstructure 620 can include a glass layer 622 that can serves as an outersurface member for a portion of the multi-layer housing structure 620. Alamination layer 624 can be provided between the glass layer 622 and asecond glass layer 626. The lamination layer 624 can serve to bondtogether a bottom layer of the first glass layer 622 and a top surfaceof the second class layer 626. In addition, a second lamination layer628 can be provided between the second glass layer 626 and a polymerlayer 630. The lamination layer 628 can serve to bond together a bottomlayer of the second class layer 626 and a top layer of the polymer layer630.

FIG. 6C is a simplified view of a multi-layer housing structure 640according to another embodiment. The multi-layer housing structure 640includes one glass layer and two distinct polymer layers that arelaminated together to form a multi-layer structure that can be used aspart of a housing for an electronic device. The multi-layer housingstructure 640 can include a glass layer 642 that can serves as an outersurface member for a portion of the multi-layer housing structure 640. Alamination layer 644 can be provided between the glass layer 642 and afirst polymer layer 646. The lamination layer 644 can serve to bondtogether a bottom layer of the first glass layer 642 and a top surfaceof the first polymer layer 646. In addition, a second lamination layer648 can be provided between the first polymer layer 646 and a secondpolymer layer 650. The lamination layer 648 can serve to bond together abottom layer of the first polymer layer 646 and a top layer of thesecond polymer layer 650.

FIG. 7 is a cross-sectional view of an electronic device housing 700according to one embodiment. In one embodiment, the electronic devicehousing 700 can incorporate a multi-layer structure as discussed above.

The electronic device housing 700 includes a housing 702. The housing702 include a side member 704 and a bottom member 706. A multi-layertranslucent member 708 can be provided as a top surface for theelectronic device housing 700. For example, the multi-layer translucentmember 708 can be a multi-layer structure, often referred to as a coverglass, which can include at least one glass layer (glass member) and mayalso include at least one polymer-based layer (polymer-based member).For example, the polymer-based layer(s), if provided, can be formed ofplastic. In different embodiment, the multi-layer translucent member 708can be implemented as shown in FIGS. 1, 5 and 6A-6C.

The electronic device housing 700 can include a display screen assembly710. The display screen assembly 710 can be secured to a bottom surfaceof the translucent member 708 by a layer of adhesive 812 (e.g.,translucent adhesive). The display screen assembly 710 can include oneor a plurality of distinct technology components that can be laminatedtogether. In one implementation, the technology components can, forexample, include a sensing layer (e.g., touch sensors), a displaytechnology layer (e.g., LCD panel) and/or a backlight layer. In anotherimplementation, the technology components can, for example, include anorganic light emitting diode (OLED) panel with or without a sensinglayer (e.g., touch sensors).

In addition, however, the electronic device housing 700 depicts oneembodiment of the display screen assembly 710 has having at least three(3) distinct technology layers, namely, a Liquid Crystal Display (LCD)panel layer 710 a (e.g., TFT LCD), a touch sensing layer 710 b and abacklight layer 710 c. These layers themselves can include multiplelayers or additional layers can also be present, such as polarizers,color filters, etc.

An internal space 718 is provided internal to the electronic devicehousing 700 whereby various electrical components (e.g., includingprocessor, memory, battery and circuit board) can be attached, affixedor placed so as to provide electronic operations for the electronicdevice.

In general, the various members, parts or assemblies of the electronicdevice housing 700 can be formed of any of a variety of materials, e.g.,glass, polymers or metal. In one embodiment, the multi-layer translucentmember 708 is at least partially formed of glass, and the housing 702 isformed from glass, polymer (e.g., plastic) or metal.

Additionally, it should be understood that one or more of the layers ofthe display screen assembly 710 could be integrated with the multi-layertranslucent member 708. In one example, the LCD panel layer 710 a couldbe integrated with the multi-layer translucent member 708 such as bybeing bonded (e.g., laminated) to the bottom surface of the multi-layertranslucent member 708. In another example, the LCD panel layer 710 aand the touch sensing layer 710 b could be integrated with themulti-layer translucent member 708 such as by being successively bonded(e.g., laminated) to the bottom surface of the multi-layer translucentmember 708. In still another example, the LCD panel layer 710 a, thetouch sensing layer 710 b and the backlight layer 710 c could beintegrated with the multi-layer translucent member 708 such as by beingsuccessively bonded (e.g., laminated) to the bottom surface of themulti-layer translucent member 708. An adhesive layer can be used tosecure any of the remaining layers of the display screen assembly 710not integrated to the multi-layer translucent member 708 throughlamination.

FIG. 8 is a perspective diagram of a handheld electronic device 800according to one embodiment. The handheld electronic device 800 mayinclude a housing 802, e.g., a periphery member, that is arranged to atleast partially surround the periphery of the handheld electronic device800 to form some or all of the outer-most side, top and bottom surfacesof the handheld electronic device 800. The handheld electronic device800 also includes a cover piece 804 that is arranged to be substantiallycoupled to housing 802 to effectively enclose an inner volume of thehandheld electronic device 800. The cover piece 804 may include amulti-layer transparent member 806, e.g., cover glass provided over adisplay of the handheld electronic device 800. In one embodiment, thecover piece 804 includes a protective frame 808 in which the multi-layertransparent member 806 is held. The multi-layer transparent member 806can serve as the top surface of the housing 802. A display region 807 ofthe multi-layer transparent member 806 is that portion of themulti-layer transparent member 806 that corresponds to the display(e.g., active display region). Using the techniques described herein,the multi-layer transparent member 806 can include at least one glasslayer and at least one transparent layer (glass or polymer) bondedtogether.

The housing 802 may have any suitable shape, including, for example, oneor more elements that may be combined to form a rectangular structure.The housing 802 may at least partially enclose an inner volume in whichelectronic device components may be assembled and retained. The shape ofthe housing 802 may substantially define boundaries of the inner volume,and may be determined based upon the size and type of components placedwithin the inner volume.

The housing 802 may have any suitable size, and the size may bedetermined based on any suitable criteria. Suitable criteria mayinclude, but are not limited to including, aesthetics or industrialdesign, structural considerations, components required for a desiredfunctionality, and/or product design. The housing 802 may have anysuitable cross-section, including for example a variable cross-sectionor a constant cross-section. In some embodiments, the cross-section maybe selected based on desired structural properties for the housing 802.For example, the cross-section of housing 802 may be substantiallyrectangular, such that the height of the housing 802 is substantiallylarger than the width of the housing 802. Such a cross-sectional shapemay provide structural stiffness in compression and tension, as well asin bending. In some embodiments, the dimensions of the housing 802cross-section may be determined relative to the dimensions of thecomponents contained by housing 802.

In some embodiments, the housing 802 may include features 810. Thefeatures 810 may generally include one or more openings, knobs,extensions, flanges, chamfers, or other features for receivingcomponents or elements of the device. The features 810 of the housing802 extend from any surface of housing 802, including for example frominternal surfaces, e.g., to retain internal components or componentlayers, or from external surfaces. In particular, the housing 802 mayinclude a slot or opening (not shown) for receiving a card or traywithin the handheld electronic device 800. The housing 802 may alsoinclude a connector opening (not shown), e.g., for a 30-pin connector,through which a connector may engage one or more conductive pins of thehandheld electronic device 800. Other features 810 included on thehousing 802 may include, but are not limited to, an opening forproviding audio to a user, an opening for receiving audio from a user,an opening for a connector (e.g., audio connector or power supplyconnector), and/or features for retaining and enabling a button such asa volume control or silencing switch.

As noted above, the electronic device can be a handheld electronicdevice or a portable electronic device. The invention can serve toenable a glass cover to be not only thin but also adequately strong.Since handheld electronic devices and portable electronic devices aremobile, they are potentially subjected to various different impactevents and stresses that stationary devices are not subjected to. Assuch, the invention is well suited for implementation of glass surfacesfor handheld electronic device or a portable electronic device that aredesigned to be thin.

The strengthened glass, e.g., glass covers or cover windows, isparticularly useful for thin glass applications. For example, thethickness of a glass cover being strengthened can be between about0.5-2.5 mm. In other embodiments, the strengthening is suitable forglass products whose thickness is less than about 2 mm, or even thinnerthan about 1 mm, or still even thinner than about 0.6 mm.

In one embodiment, the size of the glass cover depends on the size ofthe associated electronic device. For example, with handheld electronicdevices, the size of the glass cover is often not more than five (5)inches (about 12.7 cm diagonal. As another example, for portableelectronic devices, such as smaller portable computers or tabletcomputers, the size of the glass cover is often between four (4) (about10.2 cm) to twelve (12) inches (about 30.5 cm) diagonal. As stillanother example, for portable electronic devices, such as full sizeportable computers, displays (including televisions) or monitors, thesize of the glass cover is often between ten (10) (about 25.4 cm) totwenty (20) inches (about 50.8 cm) diagonal or even larger.

However, it should be appreciated that with larger screen sizes, thethickness of the glass layers may need to be greater. The thickness ofthe glass layers may need to be increased to maintain planarity of thelarger glass layers. While the displays can still remain relativelythin, the minimum thickness can increase with increasing screen size.For example, the minimum thickness of the glass cover can correspond toabout 0.3 mm for small handheld electronic devices, about 0.5 mm forsmaller portable computers or tablet computers, about 1.0 mm or more forfull size portable computers, displays or monitors, again depending onthe size of the screen. However, more generally, the thickness of theglass cover can depend on the application and/or the size of electronicdevice.

As discussed above, glass cover or, more generally, a glass piece may bechemically treated such that surfaces of the glass are effectivelystrengthened. Through such strengthening, glass pieces can be madestronger so that thinner glass pieces can be used with consumerelectronic device. Thinner glass with sufficient strength allows forconsumer electronic device to become thinner.

The techniques describe herein may be applied to glass surfaces used byany of a variety of electronic devices including but not limitedhandheld electronic devices, portable electronic devices andsubstantially stationary electronic devices. Examples of these includeany known consumer electronic device that includes a display. By way ofexample, and not by way of limitation, the electronic device maycorrespond to media players, mobile phones (e.g., cellular phones),PDAs, remote controls, notebooks, tablet PCs, monitors, all in onecomputers and the like.

In general, the steps associated with the methods described herein mayvary widely. Steps may be added, removed, altered, combined, andreordered without departing from the spirit or the scope of theinvention.

The various aspects, features, embodiments or implementations of theinvention described above can be used alone or in various combinations.

Additional details on strengthening edges of glass articles and/ordifferent chemical baths can be found in: (i) U.S. Provisional PatentApplication No. 61/156,803, filed Mar. 2, 2009 and entitled “TECHNIQUESFOR STRENGTHENING GLASS COVERS FOR PORTABLE ELECTRONIC DEVICES”, whichis herein incorporated by reference; (ii) International PatentApplication No. PCT/US2010/025979, filed Mar. 2, 2010 and entitled“Techniques for Strengthening Glass Covers for Portable ElectronicDevices”, which is herein incorporated by reference; (iii) U.S.Provisional Patent Application No. 61/374,988, filed Aug. 18, 2010, andentitled “ENHANCED STRENGTHENING OF GLASS”, which is hereby incorporatedherein by reference; (iv) U.S. patent application Ser. No. 12/895,823,filed Sep. 30, 2010 and entitled “ENHANCED STRENGTHENING OF GLASS”; (v)U.S. patent application Ser. No. 12/895,372, filed Sep. 30, 2010 andentitled “TECHNIQUES FOR STRENGTHENING GLASS COVERS FOR PORTABLEELECTRONIC DEVICES”, which is herein incorporated by reference; (vi)U.S. patent application Ser. No. 12/895,393, filed Sep. 30, 2010 andentitled “TECHNIQUES FOR STRENGTHENING GLASS COVERS FOR PORTABLEELECTRONIC DEVICES”, which is herein incorporated by reference; (vii)Provisional Patent Application No. 61/301,585, filed Feb. 4, 2010 andentitled “TECHNIQUES FOR STRENGTHENING GLASS COVERS FOR PORTABLEELECTRONIC DEVICES,” which is hereby incorporated herein by reference;(viii) U.S. Provisional Patent Application No. 61/410,290, filed Nov. 4,2010, and entitled “ENHANCED STRENGTHENING OF GLASS”, which is herebyincorporated herein by reference; (ix) PCT International Application No.PCT/US2011/023499, filed Feb. 2, 2011, and entitled “ENHANCED CHEMICALSTRENGTHENING GLASS OF COVERS FOR PORTABLE ELECTRONIC DEVICES”, which ishereby incorporated herein by reference; (x) U.S. patent applicationSer. No. 12/847,926, filed Jul. 30, 2010, and entitled “ELECTRONICDEVICE HAVING SELECTIVELY STRENGTHENING GLASS COVER GLASS”, which ishereby incorporated herein by reference; (xi) U.S. Provisional PatentApplication No. 61/453,404, filed Mar. 16, 2011, and entitled“ELECTRONIC DEVICE HAVING SELECTIVELY STRENGTHENED GLASS”, which ishereby incorporated herein by reference; and (xii) U.S. patentapplication Ser. No. 13/235,090, filed Sep. 16, 2011, and entitled“ELECTRONIC DEVICE HAVING SELECTIVELY STRENGTHENED GLASS”, which ishereby incorporated herein by reference.

Additional details on compact housing configurations for portableelectronic device can be found in: (i) U.S. patent application Ser. No.13/246,707, filed Sep. 27, 2011, and entitled “HOUSING FOR PORTABLEELECTRONIC DEVICE WITH REDUCED BORDER REGION”, which is hereinincorporated by reference; and (ii) U.S. patent application Ser. No.13/246,697, filed Sep. 27, 2011, and entitled “HOUSING FOR PORTABLEELECTRONIC DEVICE WITH REDUCED BORDER REGION”, which is hereinincorporated by reference.

Although only a few embodiments of the invention have been described, itshould be understood that the invention may be embodied in many otherspecific forms without departing from the spirit or the scope of thepresent invention. By way of example, the steps associated with themethods of the invention may vary widely. Steps may be added, removed,altered, combined, and reordered without departing from the spirit ofthe scope of the invention. Similarly, while operations are depicted inthe drawings in a particular order, this should not be understood asrequiring that such operations be performed in the particular ordershown or in sequential order, or that all illustrated operations beperformed, to achieve desirable results.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of the disclosure or of what maybe claimed, but rather as descriptions of features specific toparticular embodiment of the disclosure. Certain features that aredescribed in the context of separate embodiments can also be implementedin combination. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations, one or more features from a claimed combination can insome cases be excised from the combination, and the claimed combinationmay be directed to a subcombination or variation of a subcombination.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents, which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and apparatuses of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutations,and equivalents as fall within the true spirit and scope of the presentinvention.

What is claimed is:
 1. A housing for an electronic device comprising: amulti-layer cover for the housing including: a first glass layer havinga first level of chemical strengthening to a first depth of layer anddefining at least a portion of an external surface of the electronicdevice; and a second glass layer bonded to the first glass layer andhaving a second level of chemical strengthening different from the firstlevel of chemical strengthening, the second level of chemicalstrengthening to a second depth of layer that is less than the firstdepth of layer; and a glass housing structure defining an opening andhaving sides and a bottom defining at least a portion of the externalsurface of the electronic device, the multi-layer cover positioned overthe opening in the glass housing structure.
 2. The housing of claim 1,wherein the housing further comprises a lamination layer positionedbetween the first glass layer and the second glass layer.
 3. The housingof claim 2, wherein the first glass layer, the second glass layer, andthe lamination layer are transparent.
 4. The housing of claim 1, whereinthe multi-layer cover further comprises an additional layer bonded tothe second glass layer.
 5. The housing of claim 4, wherein theadditional layer is a glass layer.
 6. The housing of claim 4, whereinthe additional layer is a polymer layer.
 7. A housing for an electronicdevice comprising: a front cover member for the housing including: afirst layer including a first chemically strengthened glass materialhaving a first inner surface and a first outer surface, the first outersurface defining at least a first portion of an exterior surface of thehousing and having a first compressive stress; and a second layerincluding a second chemically strengthened glass material having asecond inner surface and a second outer surface, the second innersurface having a second compressive stress that is less than the firstcompressive stress; and a housing structure having glass sides and abottom and defining at least a portion of an interior volume and asecond portion of the exterior surface of the housing, the second innersurface of the front cover member coupled to the glass sides of thehousing.
 8. The housing of claim 7, wherein the second outer surface isbonded to the first inner surface.
 9. The housing of claim 8, furthercomprising a lamination film bonded to the second outer surface and thefirst inner surface.
 10. The housing of claim 7, further comprising athird layer including a transparent material having a third innersurface and a third outer surface, the third outer surface being bondedto the first inner surface.
 11. The housing of claim 10, furthercomprising a first lamination film bonded to the third outer surface andthe first inner surface and a second lamination film bonded to the thirdinner surface and the second outer surface.
 12. The housing of claim 7,wherein: the first layer has a thickness from 0.5 mm to 2.5 mm; and thesecond layer has a thickness from 0.5 mm to 2.5 mm.
 13. An electronicdevice housing comprising: a glass housing structure having sides and abottom formed from glass and defining at least a first portion of anexterior surface of the electronic device housing; and a cover structureattached to the glass housing structure and comprising: a first glasslayer having a first compressive stress profile with a first depth, thefirst glass layer defining at least a second portion of the exteriorsurface of the electronic device housing; and a second glass layerbonded to the first glass layer and having a second compressive stressprofile with a second depth that is less than the first depth.
 14. Theelectronic device housing of claim 13, wherein the first compressivestress profile has a first surface compressive stress and the secondcompressive stress profile has a second surface compressive stress, thesecond surface compressive stress being greater than the first surfacecompressive stress.
 15. The electronic device housing of claim 13,wherein the cover structure is substantially transparent.
 16. Theelectronic device housing of claim 13, wherein the cover structurecomprises a display region.
 17. The electronic device housing of claim13, wherein: the first glass layer has a thickness less than or equal to1 mm; and the second glass layer has a thickness less than or equal to 1mm.